U.S. Secretary of State Marco Rubio said there are "good signs" in ongoing negotiations with Iran but warns Washington has "other options" if diplomacy fails.

"There are some good signs,” Rubio told reporters but said: "I don't want to be overly optimistic, as well. So, let's see what happens over the next few days."

In talks with Iran, "I think we've made some progress,” Rubio said. "But obviously we're dealing with a system that itself is a little fractured.”

He said U.S. President Donald Trump’s preference was to "do a good deal.”

"It's always been his preference. If we can get a good deal done, that would be great. I'm not here to tell you that it's going to happen for sure, but I'm here to tell you that we're going to do everything we can to see we can get one,” Rubio said.

"But if we can't get a good deal, the president's been clear; he has other options. I'm not going to elaborate on what those are, but everybody knows what those are. But his preference is always a deal. His preference is always an agreement. His preference is always diplomacy,” he added.

Regional tensions have escalated since the U.S. and Israel launched strikes against Iran on Feb. 28. Tehran retaliated with strikes targeting Israel as well as U.S. allies in the Gulf, along with the closure of the Strait of Hormuz.

A cease-fire took effect April 8 through Pakistani mediation, but talks in Islamabad failed to produce a lasting agreement. Trump later extended the truce indefinitely while maintaining a blockade on vessels traveling to or from Iranian ports through the Strait of Hormuz.